The purpose of this work is to document the polyploidization of pancreatic B-cells and exocrine cells of C57BL/KsJ - dbm and mdb mice and their normal controls. By combining microdensitometry of Feulgen stained muclei with semi-automatic nuclear size analysis, a significant increase in polyploidization of B-cells has been shown to exist in diabetics at 4.5 weeks of age relative to controls. This increment becomes greater at 12 weeks of age. In the exocrine tissue of the mouse, the degree of polyploidization is much higher than in the islets (no polyploidization of exocrine cells is seen in humans) and it is the normals, not the diabetics, which show an increase with age in teleinsular areas. Studies on liver polyploidization to determine if the effect is specific for pancreas will be continued. Also proposed are studies on the pancreas of preweanling diabetics to determine when the advanced polyploidization emerges in relation to the hyperinsulinemia demonstrated by others. Ameliorization of diabetic symptoms by restricted feeding will be studied to determine the relationship between polyploidization and hyperinsulinemia, hyperglycemia and body fat. Insight into cause and effect relationships between polyploidization and diabetic symptoms may be gained.